awk - how to get difference of the same column when other column matches

Shell Programming and Scripting
1

I have a file like this :

# cat list
cucm, location,76,2
cucm1,location1,76,4
cucm,location,80,8
cucm1,location1,90,8
cucm1,location1,87,11
cucm,location,67,9

and I want output like this :

cucm,location,76,2
cucm1,location1,76,4
cucm,location,80, 6 ===> (8-2 =6)
cucm1,location1,90,4 ====>(8-4=4)
cucm1,location1,87,3
cucm,location,67,1

Only when the first and second column matches, I should take a difference of fourth column in the consecutive matching rows.

How will I achieve it. ?

I tried this :

awk -F"," '/cucm1,location1/ {print $1, $2, $3, $4, $4-prev;prev=$4;}' list

This works. But i may not know the contents in the runtime. Hence it has to check if column1 and column2 matches and then do a diff.

Please help

2

Please use

CODE tags first
3 
awk -F"," '/cucm1,location1/ {print $1, $2, $3, $4, $4-prev;prev=$4;}' list
4

Does not seem to match what happens in the output. Too hard to understand what you are trying to do.

5

Assuming the space before the 2nd column in the input file(line 1) is a typo:

awk -F, '{x=$4;$4-=a[$1$2];a[$1$2]=x;}1'  OFS=, file

If not a typo, use this:

awk -F, '{gsub(/^ */,"",$2);x=$4;$4-=a[$1$2];a[$1$2]=x;}1'  OFS=, file

Guru.

6

Thanks a lot, Guru.
It works.
Thanks again.

Can you please explain your code snippet ?

---------- Post updated at 04:20 AM ---------- Previous update was at 03:54 AM ----------

How will I do if i have to find out the delta of multiple columns.
Thanks in Advance